What are the concentrations of PAHs in runoff from sealed and unsealed parking lots?
Concentrations of PAHs in particles (including abraded sealcoat along with urban dust and other sediment) washed off from each of the different surface types—including the unsealed parking lots—were greater than the PEC of 22.8 mg/kg. The average concentration in particles washed off parking lots that were not sealcoated was 54 mg/kg. This is not surprising because runoff from parking lots is likely to contain PAHs from many sources, including leaking motor oil, tire particles, vehicle exhaust, and atmospheric deposition. Concentrations of PAHs were much higher in particles in runoff from parking lots sealed with coal-tar based sealcoat than from all other types of parking lot surfaces. Specifically, the average concentration of PAHs from coal-tar sealed lots was 3,500 mg/kg, about 65 times higher than the average concentration in particles washed off unsealed parking lots. The average concentration in particles washed off parking lots sealed with asphalt-based sealcoat was 620 mg/kg,
